1. Field of the Invention
The present invention relates to an inkjet head that ejects ink from ejection ports.
2. Description of Related Art
An inkjet head that ejects ink by an inkjet system includes nozzles for ejecting ink, a common ink chamber for supplying ink to be ejected from the nozzles, and individual ink passages leading from outlets of the common ink chamber to the ejection ports of the respective nozzles. In the inkjet head, part of each individual ink passage is formed into a pressure chamber. An actuator is provided for each pressure chamber to change the volume of the pressure chamber. An ejection pulse as a voltage signal is given to the actuator to deform the actuator. Due to the deformation of the actuator, pressure is applied to ink in the pressure chamber. As a result, ink is ejected from the corresponding nozzle. At this time, the pressure applied to ink in the pressure chamber induces a pressure wave, the medium for which is ink, in the individual ink passage. Japanese Patent Unexamined Publication No. 2003-305852 discloses an inkjet head that efficiently ejects ink by using proper oscillation in the individual ink passage due to the pressure wave. The inkjet head of the publication adopts a so-called fill-before-fire method, in which the volume of each pressure chamber is once increased and then the pressure chamber is restored to its original volume at a timing when the pressure in the pressure chamber becomes high because of the proper oscillation in the corresponding individual ink passage, to apply large ejection pressure to ink.